A large amount of expanded polystyrene has been used in trading site as material for containers of wide variety of products, such as foods and so forth. In a fish market, fruit and vegetable market and so forth, a large amount of expanded polystyrene containers are disposed everyday. Upon thermal disposal of such disposed expanded polystyrene, problems are encountered not only in generation of black smoke with offensive odor resulting in pollution of the environmental air but also in generation of high temperature heat during thermal disposal possibly resulting in damaging of an incinerator. Therefore, upon disposal in the market or so forth, a thermal welting machine for melting the expanded polystyrene container by blowing hot air has been employed. However, even in this case, due to fag end, such as scales or bones of fish and so forth that adhere to the surface of a container made of expanded polystyrene, strong offensive odor tends to be generated.
Therefore, in the recent years, disposal treatment in a trading site, such as a fish market, fruit and vegetable market and so forth is avoided as much as possible and the disposed expanded polystyrene containers are transported to disposal equipment to perform disposal treatment such as thermal disposal or reduction into oil and so forth. On the other hand, in the recent years, trend to recycling of the expanded polystyrene is growing. Namely, an expanded polystyrene recycling association, in which manufacturers are involved, has been established and over hundred of disposal and recycling facilities, called as FC plaza, have been constructed in various places throughout the country. According to recent information, a law is going to be established to make collection and recycling activity involving the manufacturers as a major party, as a duty.
Expanded polystyrene has a large volume per unit weight for containing a large amount of air to encounter a problem of high transportation cost in transportation to the disposal and recycling facility. Namely, while the specific gravity of polystyrene resin (styrene) before foaming is a value slightly smaller than 1, the specific gravity of expanded polystyrene becomes about 0.02 for expansion of volume to be fifth times greater through foaming process which can be said as mixing with air. Therefore, a truck having a capacity for transporting 1 ton of waste material, may transport only 20 kg of expanded polystyrene. In other words, in order to transport 20 kg of polystyrene, fifty times of volume of air has to be transported simultaneously.
Therefore, there has been proposed a two stage treatment process, in which expanded polystyrene is dissolved in a limonene, as by-product in manufacturing of orange juice or so forth to generate an intermediate product with reduced volume at the trading site, such as a market or so forth, and the intermediate product is transported final treatment facility to perform final treatment. For detail of the recycling method utilizing limonene, see "Sanpai Times", Oct. 26, 1994 and so forth.
Since the foregoing two stage treatment method encounters the following problems for use of limonene as organic solvent.
At first, since limonene is natural produce extracted from peel of citrus fruit, such as orange or so forth, supply amount is limited and expensive.
Secondly, the intermediate produce of limonene and polystyrene increases viscosity according to increasing of polystyrene content, and in particular, when polystyrene content becomes greater than or equal to 40%, the intermediate produce becomes viscous like millet jelly to be difficult to handle.
Thirdly, since viscosity of the mixture is increased according to increasing of dissolving amount of polystyrene in limonene, subsequent dissolving speed of polystyrene is gradually lowered. Therefore, treatment period can be prolonged.
Fourthly, since limonene has low stability, reaction, such as polymerization or so forth can be caused in heating for separation and regeneration of polystyrene from the intermediate produce by distillation to generate irritating odor specific to limonene from the regenerated polystyrene and whereby to degrade quality of the regenerated polystyrene.
Accordingly, it is an object of the present invention to provide a method for treating expanded polystyrene which can use inexpensive organic solvent, generate the intermediate produce with low viscosity at short period and a high quality polystyrene can be regenerated from the intermediate product.